The present invention is related to a tubing rotator and specifically to a tubing rotator for rotating a tube mounted on a hanger within a wellhead.
A tubing string is fitted in well casing head for providing a conduit for a pump jack rod coupled to a pump jack that is used to pump fluids out of the well. The tubing string is mounted within the well casing head on a hanger landed in the casing head. After the tubing string is mounted, a housing having a central opening is mounted on the casing head enclosing the tubing string within the casing head. The pump jack rod extends outside of the housing through the axial opening.
With use, the rod engages the sidewall of the tubing string leading to wear and failure of the tubing string. To prolong the life of the tubing string, tubing rotators are used for rotating the tubing string during the pumping action of the rod, i.e., the up and downward movement of the rod. In this regard, during pumping, the rod makes contact with different areas of the tubing string and as such wear is not concentrated in a single area of the tubing string, thus prolonging the life of the tubing string.
Current rotating mechanisms used to rotate tubing strings are installed into the well casing head after the tubing hanger is completely installed. Consequently, additional service personnel are required to install the rotating mechanism after installation of the hanger. Some rotating mechanisms even offset the location of the housing. Consequently, the length of the linkage driving the pump rod has to be altered.
Consequently, a rotating mechanism is desired that can be easily installed after the hanger has been landed, which does not offset the location of the housing and which allows for a larger diameter tubing rotating gear to be installed thereby providing for greater gear reduction and as such, requiring less force for rotating the gear and thus, the tubing string.
A tubing rotator is provided which is incorporated in the housing coupled on a well casing head. The rotator comprises a first gear fitted within the housing and having an axial opening a portion of which is polygonal. A tubing mandrel (also referred to herein as the xe2x80x9cmandrelxe2x80x9d for convenience) is coupled to the tubing string. The tubing mandrel has a portion of its outer surface that is also polygonal and is preferably complementary to the polygonal portion of the gear axial opening. A retainer retains the gear within the housing. A second gear, as for example a worm gear preferably having a spiral tooth is transversely fitted within the housing and is coupled to the first gear, i.e., the teeth of the first gear mesh with the teeth of the second gear. Consequently, rotation of the second gear causes rotation of the gear and thereby rotation of the mandrel. The second gear is coupled with a handle which is coupled to a pump jack. The handle is coupled to the second gear preferably by clutch such as a friction clutch or by a ratchet mechanism. In this regard, movement of the handle in one direction causes rotation of the second gear whereas movement in the opposite direction does not cause rotation the second gear.
In an exemplary embodiment, where the second gear is a worm gear, the teeth of the first gear meshed with the tooth of the worm gear as well as the troughs between the first gear teeth are curved having a curvature that is complementary to the curvature of the gear tooth formed on the worm gear. In this regard, a larger surface area of the first gear teeth make contact with the worm gear tooth thereby allowing for more force generated by the rotation of the worm gear to be transferred to the first gear for rotating the mandrel.